The present invention concerns lifting loops or slings designed to lift goods, particularly heavy goods, of the kind comprising a core of parallel threads or yarns which are covered by a protecting cloth.
Lifting slings of this kind are generally manufactured by arranging a strip of cloth about a core of the kind mentioned, whereupon the edges of the strip are sewn together along a generatrix of the essentially cylindrically shaped sling thus formed, whereby the core will be tightly enclosed by the cloth. Because the conditions of use of the sling make it particularly desirable that the seam does not project beyond the remainder of the periphery of the sling, the sewing together is effected manually, rendering the manufacture of slings of this kind rather expensive.
According to prior-art manufacturing methods flat lifting slings are produced by arranging a protective cover about a flat core of threads or yarns and, instead of sewing together the protective cover joints directly edge to edge by a seam interconnecting the cover edges in the manner equivalent to that of a hand-sewn sling, thereafter covering the gap formed between the strip edges on one of the flat sides of the sling with a further strip which covers the gap and is narrower than the width of the strip, and then sewing this narrower strip to the rest of the sling by stitches passing through the sling. Such a flat sling, although possessing the advantage of allowing the sewing work to be performed on a machine, suffers from considerable disadvantages in use, particularly because the seams, on account of their positions on the sling and the design of the latter as a whole, are exposed to wear which fairly rapidly makes the sling unfit for use.